000
FXUS62 KRAH 011718
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
115 PM EDT SAT AUG 1 2015
.SYNOPSIS...A WEAK SURFACE FRONT WILL WAVER OVER EASTERN NORTH
CAROLINA THROUGH SUNDAY WHILE WEAK HIGH PRESSURE WILL EXTEND INTO
THE PIEDMONT.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
AS OF 1050 AM SATURDAY...
LIGHT BUT PERSISTENT NLY LOW LEVEL FLOW HAS FILTERED LOWER DEWPOINTS
INTO MOST OF THE PIEDMONT OF CENTRAL NC. THIS SLIGHTLY LESS HUMID
AIR WILL WORK ITS WAY EAST AND ENCOMPASS SOME OF THE SANDHILLS AND
COASTAL PLAIN THIS AFTERNOON.
AN AREA OF HIGH PRESSURE AT 850MB (A BIT STRONGER THAN PREDICTED BY
THE MODELS) EXTENDS WEST-TO-EAST ACROSS THE REGION THIS MORNING.
ALOFT...DRY W-NW FLOW NOTED THANKS TO A BROAD UPPER TROUGH OVER THE
EASTERN U.S. PRECIP WATER VALUES ARE BELOW NORMAL OVER MOST OF THE
PIEDMONT (ABOUT HALF OF NORMAL) WHILE THE PRECIP WATER VALUES IN THE
COASTAL PLAIN AND SANDHILLS ARE CLOSE TO NORMAL. THE RELATIVELY DRY
AND STABLE (FOR SUMMER) AIR MASS WILL INHIBIT CONVECTIVE DEVELOPMENT
THIS AFTERNOON FOR MOST OF THE REGION. THE EXCEPTION WILL BE THE FAR
SE WHERE BETTER MOISTURE AND INSTABILITY MAY TRIGGER AN ISOLATED
SHOWER OR STORM LATE THIS AFTERNOON-EARLY EVENING.
WHILE IT WILL BE HOT THIS AFTERNOON WITH TEMPS IN THE 90-95 DEGREE
RANGE...SFC DEWPOINTS IN THE 50S-LOWER 60S WILL HELP TO TAKE THE
EDGE OFF THE HEAT.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 255 AM FRIDAY...
LITTLE CHANGE TO THE FORECAST IN THE LONG TERM. THE UPPER LEVEL
PATTERN REMAINS FAIRLY STAGNANT WITH UPPER RIDGE OVER THE SOUTHWEST
CONUS AND EAST COAST UPPER TROUGH THAT WILL GRADUALLY RELAX THROUGH
THE SHORT TERM. AN UPPER LOW AND REFLECTED SURFACE LOW WILL RESIDE
NORTH OF THE GREAT LAKES BUT WILL BE OF LITTLE CONSEQUENCE TO THE
AREA WHILE SEVERAL SHORTWAVE IMPULSES SKIRT THROUGH THE MID-ATLANTIC
STATES...REMAINING MAINLY NORTH OF THE FORECAST AREA. ANY CONVECTION
WILL BE DIURNALLY DRIVEN BUT MOISTURE AND PRECIPITABLE WATER VALUES
ARE VERY LOW FOR THIS TIME OF YEAR...GENERALLY LESS THAN 1.5 INCHES.
A SURFACE HIGH IN THE WESTERN ATLANTIC WILL BRING WEAK SOUTHWESTERLY
RETURN FLOW OVER THE AREA. THIS WILL HELP HIGH TEMPERATURES WARM
INTO THE MID 90S WITH SOME UPPER 90S POSSIBLE ACROSS THE SOUTH BY
TUESDAY AFTERNOON. LOWS MAINLY IN THE UPPER 60S IN THE NW PIEDMONT
TO LOWER 70S ELSEWHERE.
&&
.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 255 AM SATURDAY...
WEDNESDAY AND WEDNESDAY NIGHT: FORECAST BECOMES LESS CONFIDENT ON
WEDNESDAY AS MODELS SHOW A SHORTWAVE WEST OF THE AREA THAT HELPS TO
CAUSE A SOUTHWARD PUSH IN THE UPPER LEVEL PATTERN. THE EXACT
LOCATION OF THE SHORTWAVE IS IN QUESTION WITH THE GFS DEVELOPING A
STRONG WAVE IN THE OHIO VALLEY BUT THE ECMWF IS WEAKER WITH THE
FEATURE AND MUCH FURTHER SOUTH...ACROSS THE TENNESSEE VALLEY. THUS
THE ECMWF LENDS TO A LITTLE GREATER FORCING ACROSS CENTRAL NC FOR
AFTERNOON CONVECTION ON WEDNESDAY. IN ADDITION...HIGH PRESSURE IN
THE ATLANTIC IS CENTERED A LITTLE FURTHER SOUTH IN THE ECMWF AS WELL
AND ALLOWS A SURFACE TROUGH ASSOCIATED WITH THE CANADIAN LOW TO
BECOME MORE ACTIVE OVER THE AREA DURING THE AFTERNOON AND SERVE AS A
CATALYST FOR CONVECTION. BEST CHANCES FOR ANY SHOWER AND
THUNDERSTORM ACTIVITY WOULD BE ACROSS THE NORTH AND IN EASTERN
COUNTIES. HIGHS IN THE MID 90S AND LOWS IN THE LOW 70S.
THURSDAY AND FRIDAY: WITH UNCERTAINTIES ALREADY BUILT INTO
WEDNESDAYS FORECAST...THURSDAY AND FRIDAY ONLY BECOMES MORE
UNCERTAIN WITH REGARD TO THE EVOLUTION OF THE SHORTWAVE TO THE
WEST...THE VERY LATEST RUN OF THE ECMWF HAS FALLEN MORE IN LINE WITH
THE TIMING OF THE GFS FOR A THURSDAY NIGHT INTO FRIDAY PASSAGE OF
THE SHORTWAVE...GFS SOLUTION STILL SLIGHTLY NORTHWARD OF THE ECMWF.
REGARDLESS...MOISTURE INCREASES SIGNIFICANTLY BACK OVER 2 INCHES.
THURSDAY AFTERNOON/EVENING WILL HAVE THE BEST CHANCE FOR CONVECTION
WITH MODELS SHOWING ACTIVITY LINGERING THROUGH FRIDAY AFTERNOON AS
WELL BEFORE THE WAVE FINALLY EXITS THE COAST OVERNIGHT FRIDAY NIGHT
INTO SATURDAY MORNING. EXTRA CLOUDS AND PRECIPITATION WILL HELP
TEMPERATURES DROP BACK AT LEAST INTO THE LOW 90S IF NOT UPPER 80S BY
THE END OF THE WEEK. LOWS MAINLY IN THE LOWER 70S.
&&
.AVIATION /18Z SATURDAY THROUGH WEDNESDAY/...
AS OF 115 PM SATURDAY...
HIGH CONFIDENCE OF VFR CONDITIONS ACROSS JUST ABOUT ALL OF CENTRAL
NC FOR THE NEXT 24 HOURS. THE ONLY EXCEPTIONS WILL BE AN EXTREMELY
SMALL CHANCE OF AN ISOLATED RAIN SHOWER THIS AFTERNOON IN THE
SOUTHEASTERN COASTAL PLAIN (SOUTHEAST OF KGSB AND KFAY) AND A CHANCE
OF SOME DAYBREAK STRATUS/FOG AT KFAY AND KRWI. THE RAIN CHANCES ARE
SO SMALL TO PRECLUDE ANY MENTION OF RESTRICTIONS IN THE TAFS. THE
THREAT OF MVFR/IFR STRATUS/FOG IS LIMITED WITH ONLY A SUBSET OF
GUIDANCE INDICATING IT...MORE EMPHATICALLY AT KFAY. PROBABILITIES
ARE LOW BUT STILL CONCERNED ABOUT THE OCCURRENCE...SO WILL INCLUDE A
SHORT TEMPO GROUP TO COVER IT.
OTHERWISE...SKIES WILL BE MAINLY CLEAR WITH JUST SOME VFR CUMULUS
THIS AFTERNOON AT 4.5-6KFT AND PERHAPS SOME SCT FAIR WEATHER CUMULUS
AND CIRRUS ON SUNDAY WITH VFR CONDITIONS. SURFACE WINDS WILL BE
LIGHT THROUGH THE PERIOD...MAINLY FROM THE NORTHWEST TO NORTHEAST
ALTHOUGH A PERIOD OF LIGHT SOUTHERLY WINDS IS POSSIBLE AT KFAY AND
KRWI LATE TONIGHT AS THE SEA BREEZE BOUNDARY SHIFTS INLAND. LIGHT
MAINLY NORTHERLY WINDS ARE EXPECTED AGAIN ON SUNDAY.
LOOKING BEYOND 18Z SUN AFTERNOON... VFR CONDITIONS ARE EXPECTED TO
DOMINATE THE WEATHER ACROSS CENTRAL NC THROUGH MID WEEK. SOME PATCHY
MORNING STRATUS AND FOG IS POSSIBLE ON MONDAY AND TUESDAY MORNINGS.
THE THREAT OF SHOWERS OR THUNDERSTORMS WILL BE VERY LOW THROUGH
WEDNESDAY AND INCREASE SOMEWHAT ON THURSDAY. -BLAES
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...ELLIS
LONG TERM...ELLIS
AVIATION...BLAES